Core raw paper for corrugated boards, and method of producing the same

ABSTRACT

A method of producing core raw paper is provided that prevents corrugation cracking, corrugation cutting or breakage from occurring during corrugating operation using a corrugating roll, prevents the wearing of the corrugating roll, reduces the consumption of driving power and noise, is capable of uniformly and efficiently coating the core raw paper with wax, and does not pollute facilities such as a paper machine.  
     A method of producing core raw paper for corrugated boards coated with wax by a paper machine having a plurality of driers, comprising the steps of spraying, as at (S), the surface of a drier (C 8 ) with a dispersion containing the wax, changing the wax into oil on the surface of the heated drier (C 8 ), and pressing the surface of the drier (C 8 ) against core raw paper ( 100 ) to thereby transfer the oil-changed wax from the surface of the drier (C 8 ) to the core raw paper ( 100 ).

TECHNICAL FIELD

[0001] 1. Technical Field of the Invention

[0002] The present invention relates to core raw paper for corrugated boards, and a method of producing the same, and more particularly to core raw paper for corrugated boards, and a method of producing the same that prevents corrugation cracking, corrugation cutting or breakage from occurring during corrugating operation using a corrugating roll, prevents the wearing of the corrugating roll and reduces the consumption of driving power and noise.

BACKGROUND ART

[0003] 2. Prior Art

[0004] A corrugated board is made by cutting, folding and thus assembling core raw paper in the form of a flat board.

[0005] Core raw paper for corrugated boards is corrugated by a single phaser of a corrugator, and then is coated with a liner to form a one-sided corrugated paper sheet (liner with core raw paper), and then is coated with a back liner to form a corrugated board.

[0006] The process of forming a one-sided corrugated paper sheet in this single phaser is shown in FIG. 5.

[0007] Core raw paper 100 is pressed and corrugated at the point of engagement between a pair of corrugating rolls, i.e. an upper corrugating roll 101 and a lower corrugating roll 102 to form a corrugated core 103.

[0008] And the top of the corrugated core 103 is coated with glue by a gluing roll 104, and a liner 106 and the top of the corrugated core are pressed together between the lower roll 102 and the pressure roll 105 to form a one-sided corrugated paper sheet 107.

[0009] However, in general core raw paper is subjected to a strong tension, flexion, shear and other forces from a pair of corrugating rolls during the corrugating process, and accordingly the corrugation cracks (corrugation cracking) or is cut off (corrugation cutting) and in extreme cases core raw paper ruptures over the whole width.

[0010] In addition, the corrugating rolls always exposed to frictions with core raw paper wear off, resulting in increased consumption of driving power and louder noises.

[0011] For these reasons, the polishing cycle of the corrugating rolls become shorter and their operating efficiency falls down.

[0012] And from the viewpoint of recycling, core raw paper is currently produced mostly from recycled paper originating from waste paper.

[0013] As a result, core raw paper often contains clay and other foreign matters used in coated paper. And there are many instances where the strength of paper decreased because of the blending of so-called low-grade waste paper including discarded magazines and other paper.

[0014] Accordingly, the corrugation cracking, corrugation cutting and breakage occur more easily during the corrugating operation described above, and the corrugating rolls tend to wear more quickly because of clay and other ash contents contained in core raw paper.

[0015] In view of these facts, the method of directly coating core raw paper with wax was developed as a method of enhancing paper strength and reducing the friction with the corrugation rolls.

[0016] For example, there is a method of coating both the face and back of core raw paper with solid wax by pinching and pressing core raw paper between a pair of solid wax holders (upper and lower was holders). (See Japanese Patent Application Laid Open 4-47930)

[0017] However, as too much wax is transferred from core raw paper to the corrugating roll because too much wax was applied on core raw paper, wax carbonizes on the surface of the corrugating roll normally heated to around 160-190° C.

[0018] Thus, the quality of core raw paper diminishes due to a black stripe that has developed on the corrugated core or because of some stains on the liner.

[0019] In addition, there was a disadvantage in that the carbonized wax filled small holes for vacuum created on the surface of the corrugating roll.

[0020] Therefore, a method was developed for applying wax on core raw paper by spraying a lubricant in the form of a solution containing wax or in the form of a dispersion on the same.

[0021] For example, Japanese Patent Application Laid Open 11-117188 discloses a method of producing core raw paper for corrugated boards wherein a lubricant is directly sprayed on core raw paper in a drier for a moisture of undried raw paper with moisture content of 10-30% during the process of paper making (normally dryness is lower than 10%).

[0022] This method leaves the lubricant on the surface without allowing the same to penetrate into the inside of the raw paper because of the dispersion of moisture from inside the raw paper during the desiccation of moisture contained in the core raw paper.

[0023] However, since such a method generates a current of air around core raw paper running straight at a high speed, the direct spraying of a lubricant over core raw paper leads to the phenomenon of lubricant blowing up violently.

[0024] As a result, the inside of the paper machine and peripheral equipment are intensely stained.

[0025] And a change in the moisture of core raw paper resulting from a temporary stoppage of the paper machine easily affects the adhesion of wax and sometimes results in an uneven distribution of wax.

[0026] Thus, this method had a disadvantage in that the application of lubricant was not always uniform and therefore the efficiency of application decreased.

[0027] (Issues that the Present Invention Tries to Solve)

[0028] The present invention was made under the background of such a situation in order to solve the above issues.

[0029] Specifically, it is an object of the present invention to provide core raw paper for corrugated boards and the method for producing the same that prevents corrugation cracking, corrugation cutting or breakage from occurring during corrugating operation using a corrugating roll.

[0030] Another object of the present invention is to provide core raw paper for corrugated boards and the method for producing the same that prevents the wearing of the corrugating roll, reduces the consumption of driving power and noise.

[0031] A further object of the present invention is to provide core raw paper for corrugated boards and the method for producing the same that is capable of uniformly and efficiently coating core raw paper with wax, and does not pollute facilities such as a paper machine.

DISCLOSURE OF THE INVENTION

[0032] (Means for Solving the Issues)

[0033] Thus, the inventor of the present invention made assiduous and intensive researches in the face of such background issues and as a result has found that it is possible to coat uniformly and efficiently the face of core raw paper with an adequate amount of wax without staining the inside of the paper machine or peripheral equipment not by directly spraying wax over core raw paper but by indirectly transferring wax to core raw paper by spraying a dispersion containing wax over a heated drier and by thus changing wax contained in the dispersion into oil or by spraying the same over a roll in contact with paper, and that wax can be transferred intensively from the drier or rolls onto the surface when core raw paper is as dry as possible, and based on this finding the inventor completed the present invention.

[0034] In other words, the present inventions relates to (1) core raw paper for corrugated boards wherein wax is applied on the face and back and the quantity of wax applied on said core raw paper is 0.1-10 mg/m².

[0035] And the present invention relates to (2) core raw paper for corrugated boards wherein the moisture content is less than 10% when the wax is applied.

[0036] And the present invention relates to (3) core raw paper for corrugated boards wherein a dispersion containing wax is sprayed over the last drier of the paper machine and the wax contained in said dispersion is transferred to core raw paper for coating thereon.

[0037] And the present invention relates to (4) core raw paper for corrugated boards wherein a dispersion containing wax is sprayed over the paper roll of the paper machine and the wax contained in said dispersion is transferred to core raw paper for coating thereon.

[0038] And the present invention relates to (5) a method of producing core raw paper for corrugated boards wherein a paper machine provided with a plurality of driers is used to apply wax and wherein a dispersion containing said wax is sprayed over the surface of the driers, the wax is changed into oil on the surface of the heated driers, and the oil-changed wax is transferred from the surface of the driers to the face of core raw paper.

[0039] And the present invention relates to (6) a method of producing core raw paper for corrugated boards wherein said drier is a drier belonging to the last group of the paper machine.

[0040] And the present invention relates to (7) a method of producing core raw paper for corrugated boards wherein said drier is the last upper or lower drier among the driers belonging to the last group.

[0041] And the present invention relates to (8) a method of producing core raw paper for corrugated boards wherein the melting point of said wax is lower than the surface temperature of the driers.

[0042] And the present invention relates to (9) a method of producing core raw paper for corrugated boards wherein wax is applied by using a paper machine provided with a paper roll, a dispersion containing said wax is sprayed on the surface of said paper roll, and said wax is transferred from the surface of said paper roll to the face of core raw paper.

[0043] And the present invention relates to (10) a method of producing core raw paper for corrugated boards wherein said wax is applied in such a way that the quantity of wax applied over core raw paper may be 0.1-10 mg/m².

[0044] And the present invention relates to (11) a method of producing core raw paper for corrugated boards wherein the moisture content of said core raw paper is less than 10% when the dispersion containing wax is sprayed.

[0045] And the present invention relates to (12) a method of producing core raw paper for corrugated boards wherein said wax, after having been transferred to the face of core raw paper, is partially transferred to the back of core raw paper by the winding operation of core raw paper

[0046] And the present invention relates to (13) a method of producing core raw paper for corrugated boards wherein paraffin wax, polyethylene wax or micro wax is used singly or by combination for said wax.

[0047] And the present invention relates to (14) a method of producing core raw paper for corrugated boards wherein said dispersion contains also a solid lubricant or a metal soap.

[0048] And the present invention relates to (15) a method of producing core raw paper for corrugated boards wherein said dispersion contain also oils.

[0049] And the present invention relates to (16) a method of producing core raw paper for corrugated boards wherein wax is applied by using a paper machine provided with a plurality of driers, a dispersion containing wax is sprayed over the surface of heated driers when the moisture content of core raw paper passing through the paper machine is less than 10%, the wax is changed into oil on the surface of the heated driers, the oil-changed wax is transferred from the surface of the driers to the face of core raw papers and the wax is applied in such a way that the amount of wax applied to core raw paper may be 0.1-10 mg/m².

[0050] And the present invention relates to (17) a method of producing core raw paper for corrugated boards wherein wax is applied by using a paper machine provided with a paper roll and a dispersion containing wax is sprayed over the surface of the paper roll, the wax is transferred to the face of core raw paper having moisture content of less than 10% and the wax is applied in such a way that the quantity of wax to core raw paper may be within a range of 0.1-10 mg/m².

[0051] And the present invention relates to (18) a wax or a dispersion containing wax to be applied on core raw paper for corrugated boards, and more particularly a wax or a dispersion containing wax to be applied on core raw paper for corrugated boards described in Items (3) or (4).

[0052] And the present invention relates to (19) a wax or a dispersion containing wax to be used for the method of producing core raw paper for corrugated boards, and more particularly a wax or a dispersion containing wax to be used for the method of producing core raw paper for corrugated boards described in Items (5) or (9).

[0053] The present invention may obviously be carried out by combining two or more specifications chosen from Items 1-4 described above and two or more methods of producing chosen from Items 4-17 described above as long as they conform to the objects of the present invention.

[0054] (Working)

[0055] By the present invention, dry core raw paper with a moisture content of less than 10% is coated with wax in the proportion of 0.1-10 mg/m² on the face and back.

[0056] When core raw paper coated with wax in such a proportion is corrugated by a corrugating roll, the friction with the corrugating roll is reduced and it becomes possible to continuously supply an adequate amount of wax for avoiding any seizure with the corrugating roll and the frictional resistance of the corrugating roll itself is reduced.

[0057] Such core raw paper is obtained by transferring the wax changed into oil on the surface of the driers onto the face of dry core raw paper with moisture content of less than 10% in the process of paper making.

[0058] Or it can be obtained by transferring the same onto the face of similarly dry core raw paper through the paper roll.

[0059] Or a part of the wax with which the face of core raw paper is coated can be further transferred to the back by winding said core raw paper still in a hot state directly on a reel drum.

[0060] (Working of the Invention)

[0061] By applying the present invention, it is possible to produce a core draw paper for corrugated boards that prevents corrugation cracking, corrugation cutting or breakage from occurring during corrugating operation using a corrugating roll,

[0062] And it also becomes possible to produce a core draw paper for corrugated boards that prevents the wearing of the corrugating roll, reduces the driving power consumption and noise.

[0063] And it becomes possible to produce a core draw paper for corrugated boards that is capable of uniformly and efficiently coating core raw paper with wax, and does not pollute equipment such as a paper machine.

BRIEF DESCRIPTION OF DRAWINGS

[0064]FIG. 1 is a schematic view of a paper machine.

[0065]FIG. 2 is an enlarged view of the vicinity of the last drier.

[0066]FIG. 3 is a view showing typically the spraying method of a dispersion.

[0067]FIG. 4 is a schematic view showing the last group of the drier part and the reel part of a paper machine.

[0068]FIG. 5 is a view showing the forming process of a one-sided corrugated paper sheet in a single phaser.

THE BEST MODE FOR CARRYING OUT THE INVENTION

[0069] (Mode for Carrying Out the Invention)

[0070] Some preferred modes for carrying out the invention will be shown below to describe the present invention by referring to drawings.

[0071] Core raw paper of the present invention is core raw paper for corrugated boards coated with wax on the face and back thereof, characterized in that the amount of wax applied on said core raw paper is in a range of 0.1-10 mg/m².

[0072] In reality, as described below, a sprayer is used to spray continuously a dispersion containing wax so that the amount of wax sprayed over the drier or the paper roll would be in a range of 0.1-10 mg/m².

[0073] However, even if a dispersion is continuously sprayed in this way, wax and other matters neither accumulate on the surface of driers or paper rolls nor are scraped by a doctor blade.

[0074] For this reason, one finds that wax sprayed on the surface of driers to a depth of 0.1-10 mg/m² is efficiently transferred onto the face of core raw paper.

[0075] For this wax, paraffin wax, polyethylene wax, micro wax, etc. are used. They are used singly or in combination.

[0076] Wax works to reduce remarkably the frictions between core raw paper and corrugating rolls when core raw paper is corrugated between corrugating rolls.

[0077] It is preferable that the amount of wax applied on core raw paper would be in a range of 0.1-10 mg/m² both on the face and the back, and more preferably in a range of 0.5-5 mg/m².

[0078] When the amount of wax applied is less than 0.1 mg/m², the effect of reducing friction will not be always obtainable, and if the amount is more than 10 mg/m², and excessive amount of wax will move onto the corrugating roll resulting often in seizures.

[0079] Core raw paper coated with wax on both the face and back can prevent corrugation cracking, corrugation cutting and breakage of core raw paper from occurring during corrugating operation by using a corrugating roll, prevent the wearing of the corrugating roll and reduce the consumption of driving power and noises.

[0080] [Outline of the Paper Machine]

[0081] To begin with, a general paper machine will be described by referring to drawings because core raw paper of the present invention is produced in the process of paper making, in other words by using a paper machine.

[0082]FIG. 1 is a schematic drawing of a paper machine.

[0083] A paper machine comprises a press part A, a drier part of which the first group—B, the last group—C and a reel part D (groups other than the first group and the last group of the drier part are omitted).

[0084] Core raw paper passes through the paper machine. In the first place, core raw paper 100 that enters the press part A is in the state of fluid pulp containing a large amount of water, and it is dehydrated and pressed by press rolls and press felts.

[0085] Then, it is driven to the drier part and it dries and become core raw paper as it passes through several tens of driers.

[0086] Normally about ten driers constitute a group, and then 3-5 groups consecutively constitute the drier part.

[0087] And in each group from the first group B through the last group C, the driers are arranged methodically and alternatively in the upper and lower rows, and upper canvases (B1 and C9) and lower canvases (B2 and C10) are fitted thereon to press against each drier from the above and the below.

[0088] The canvas is made of a relatively thin and strong cloth, for example canvas made of a synthetic resin.

[0089] And core raw paper 100 inserted in between is strongly pressed against the driers, and the heat of the drier serves to evaporate and disperse the moisture contained in core raw paper 100.

[0090] Furthermore, each drier contains a heat source inside, and normally each drier is set at a specific temperature so that temperature rises gradually from the first group B to the last group C.

[0091] Specifically, temperature setting differs depending on the paper making speed of core raw paper 100 and other factors. However, in the case of a paper making speed of 600-700 m/min., the temperature of the driers of the first group B is set within a range of 80-100° C.

[0092] And the last drier of the last group C (here the last drier C8 of the upper row) is set so that temperature may be around 120° C. Core raw paper in this area of the last drier of the upper row is normally in a dry state, in other words in a state of moisture content of less than 10%.

[0093]FIG. 2 is a schematic view showing the last group of the drier part and the reel part of the paper machine.

[0094] In the last group C, as described above, the first down to the sixth driers C1, C2, C3, C4, C5, C6, the last drier of the lower row C7 and the last drier of the upper C8 are arranged alternatively in the upper and lower rows, and the upper canvas C9 and the lower canvas C10 are pressed from above and below.

[0095] And each drier is set at a suitable temperature so that the last drier C8 is heated up to the maximum temperature of around 120° C.

[0096] After coming out of the drier part, core raw paper 100 is led directly to the reel part D to be wound up firmly on the reel drum D4 after passing through the paper rolls D2 and D3.

[0097] And between the last drier C8 and the reel drum D4, a moisture measurement device D1 is installed and monitors constantly the moisture contained in core raw paper 100.

[0098] At this stage, core raw paper 100 is normally in a dry state of a moisture content of around 7-8%.

[0099] [Spray Process of the Dispersion]

[0100] In the present invention, core raw paper is coated with wax by spraying the dispersion containing wax over the surface of the driers or paper rolls of the paper machine and by transferring the wax contained in the dispersion onto the face of core raw paper.

[0101] In other words, wax is applied indirectly through the driers instead of the traditional method of directly spraying a dispersion on core raw paper.

[0102] Here, in the first place, the application of wax through the driers will be described, and the method of passing through the paper rolls will be described later on.

[0103] In the case of applying wax through the driers, in the first place wax contained in the sprayed dispersion is heated to be transformed into oil over the surface of the heated driers, and this oil-changed wax is transferred from the surface of the driers onto the face of core raw paper.

[0104] Since wax is transferred from the driers uniformly and efficiently when core raw paper is as dry as possible, the dispersion containing wax is sprayed over the driers belonging to the last group of the paper machine.

[0105] As wax is sprayed on core raw paper to reduce frictions with the corrugating roll when it is corrugated by using a single phaser of the corrugator, there is no need to make wax penetrate deep into the interior of core raw paper and a superficial application is enough.

[0106] In other words, it is enough to rub wax onto the face of core raw paper, and on that occasion, it will be easily understood that wax tends to move more easily when core raw paper is in a drier state than in a moist state containing much water when the relationship between water and oil is considered.

[0107] Thus, wax is transferred without fail from the surface of driers to the face of core raw paper when the core raw paper is dry with a moisture content of less than 10%.

[0108] And since wax transforms into oil and disperses on the surface of the heated driers, it will be possible to coat core raw paper uniformly with wax.

[0109] In addition, since wax does not penetrate into the inside of core raw paper, wax will be used efficiently.

[0110] Under the normal paper making conditions, core raw paper passing through a paper machine dries up to a moisture content of less than 10% at the last group C of the drier part.

[0111] Accordingly, in most areas of the last group C, core raw paper has a moisture content of less than 10%. And it is preferable to spray a dispersion containing wax on the heated driers belonging to this last group and transfer wax to and coat core raw paper with said wax.

[0112] Especially at the level of the last drier, core raw paper is the driest with a moisture content of 7-8% as described earlier, and therefore it is more preferable to spray wax here.

[0113] Moreover, around this last drier there are relatively idle spaces and therefore it will be easy to install apparatuses for spraying the dispersion containing wax and it will be more convenient from the viewpoint of maintenance.

[0114] And since the face of core raw paper is coated intensively with wax as stated earlier, wax will be surely and efficiently transferred onto the surface of the corrugating roll at a later stage when the core raw paper will be corrugated by the corrugating roll.

[0115] And as a result as stated above, the wearing of the corrugating roll itself will be prevented.

[0116]FIG. 3 is an enlarged view of the vicinity of the last drier (here the last drier of the upper row is shown).

[0117] Core raw paper 100 is drawn between the last drier C8 and the canvas roll C11, and is strongly pressed by the upper canvas C9 on the surface of the last drier C8.

[0118] And it is transferred at the same pace as the last drier C8 (and the upper canvas C9) rotates, peals off from the surface of the last drier C8 when it reaches the position of the canvas roll C12 and is taken up by the reel drum D4.

[0119] On the other hand, in the zone L where core raw paper 100 is not in contact with the last drier C8, a spraying apparatus S is installed.

[0120] The spraying apparatus S may be arranged behind a doctor blade T.

[0121] However, the doctor blade is not absolutely necessary.

[0122]FIG. 4 is a schematic view of the method of spraying the dispersion.

[0123] On the frame body S2 of the spraying apparatus S, a plurality of mobile spray nozzles S1 are fitted at an interval of 1 m.

[0124] Specifically, four spraying nozzles may be fitted if the width of the last drier C8 is 4 m and five spraying nozzles may be fitted if the width is 5 m.

[0125] And travelling in both directions on the frame body S2 at a speed of for example 2 m/min., the mobile spraying nozzles sprays the dispersion containing wax towards the surface of the last drier C8.

[0126] At this time, some air current is generated by the rotation of the last drier C8. However, it is possible to prevent the dispersion from blowing up by setting the spraying speed of the dispersion from the spraying apparatus (spraying nozzle) at a sufficiently high level.

[0127] In addition, the provision of the doctor blade T mentioned above as shown in FIG. 3 can restrict the blow up of the dispersion.

[0128] So far, the case of spraying the dispersion towards the last drier C8 of the upper row has been described. However, if it is desired to apply wax on the other side of core raw paper, it is obviously possible to spray the dispersion on the last drier C7 of the lower row.

[0129] And in the case of spraying the dispersion on driers other than the last driers of the upper and lower rows, it is possible to spray the dispersion by using the spraying method shown in FIGS. 3 and 4.

[0130] [Dispersion Containing Wax]

[0131] The dispersion containing wax used the present invention will be described below.

[0132] This dispersion is a product obtained by dispersing wax into water by using a dispersant, and depending on the needs, various additives are added as described below.

[0133] With regard to this wax, as described above, it is preferable that paraffin wax, polyethylene wax, micro wax and other types of wax would be used singly or in combination.

[0134] In addition to their effectiveness for the mitigation of friction and their lower melting point than the surface temperature of the driers (approximately 50-100° C.), these waxes instantly transform into oil on the surface of driers heated to about 120° C.

[0135] And the dispersion becomes more effective when some solid lubricants or metal soaps are added thereto.

[0136] These solid lubricants and metal soaps adhere to core raw paper together with said wax and play a role in reducing the frictions with the corrugating roll when the core raw paper is corrugated by the corrugating roll.

[0137] As solid lubricants, molybdenum disulfide, tungsten disulfide, graphite fluoride, boron nitride, silicon nitride, etc. can be mentioned.

[0138] Among them, molybdenum disulfide is especially preferred because, when reduced to a fine grain of several μm order, its friction coefficient is reduced (approximately 0.04) and it is thermally and chemically stable.

[0139] As for metal soap, on the other hand, stearic acid soap is preferred.

[0140] Moreover, it is more preferable to add oils (mineral oils, silicone oil, synthetic oils, vegetable oils, animal oils, etc.) to said dispersion as exfoliants.

[0141] These oils, when applied over the driers, spread over their surface, form a film and facilitate the removal of wax, solid lubricants or metal soaps from the surface of the driers to core raw paper.

[0142] And it is obviously possible to add other suitable additives to the dispersion.

[0143] [Application Process of Wax]

[0144] As stated above, when the dispersion is sprayed over the surface of the driers by the dispersion apparatus S, the wax contained in the dispersion is transformed into oil and spreads over the surface of the driers. It then is transferred from the surface of the driers to the face of core raw paper and remains there.

[0145] Then, core raw paper is wound up on the reel drum with a regular pressure.

[0146] At this time, a part of wax is transferred from the face of core raw paper (or the face to which wax transferred from the drier) to the back thereof facing each other as a result of this winding up, and a part of wax is applied on the back of core raw paper.

[0147] This fact leads to the lubrication function that works on both the twin corrugation rolls and produces an effect of preventing wearing when the core raw paper is corrugated.

[0148] This point will be described in more details by referring to FIG. 2.

[0149] To begin with, on the surface of the rotating last drier C8, the wax contained in the dispersion that had already been applied forms a thin film.

[0150] When the dispersion is sprayed over there with the spraying apparatus S, the moisture contained in the dispersion evaporates due to the heat of the last drier C8, wax melts, transforms into oil and spreads over the film.

[0151] And while core raw paper 100 pressed against the upper canvas C9 and the last drier C8 are jointly rotating and transferring, the wax that had transformed into oil is transferred from the surface of the last drier C8 to the face of core raw paper 100, and core raw paper 100 is coated with wax.

[0152] The core raw paper 100 thus coated with wax on both sides separates itself from the last drier C8 at the position of the canvas roll C12, and after passing through the paper rolls D2 and D3, is taken up directly by the reel drum D4.

[0153] As core raw paper 100 wound up on the reel drum D4 still retains heat at this time, a part of the wax on the face of core raw paper 100 is transferred and adheres to the back of the core raw paper 100 opposite thereto.

[0154] And thus the coating of core raw paper with wax is completed.

[0155] Then, the method of coating core raw paper with wax not through the driers but through the paper rolls will be described hereafter. (See FIG. 2)

[0156] In this method, the dispersion containing wax is sprayed over the surface of the paper rolls and the wax contained in the dispersion is transferred from the surface of the paper rolls to the face of core raw paper.

[0157] As stated earlier, core raw paper is already in a dry state with its moisture content standing at about 7-8% as it passes through the paper roll D2 (similarly in the case of D3. Ditto hereinafter).

[0158] In other words, as stated earlier, it is in a state where wax can easily be transferred to its face.

[0159] In addition, core raw paper has just passed through the driers part C and maintains a high temperature of around 70° C.

[0160] Although the paper roll D2 itself is not heated, it receives heat from core raw paper and maintains a similar temperature.

[0161] Therefore, as the dispersion is sprayed over the paper roll, wax transforms into oil or at least softens. Thus, like in the case of the driers, it is possible to transfer with certainty, uniformly and efficiently wax onto the face of core raw paper.

[0162] It should be noted however that, in the case of this paper roll also, the method of spraying the dispersion, a partial transfer of wax to the back by the winding up of the core raw paper, use of paraffin wax, the addition of solid lubricants and oils to the dispersion, etc. are the same as in the case of the driers.

[0163] And it is possible to apply uniformly and efficiently wax in the same way not only to the paper rolls but also to any rolls remaining in contact with core raw paper while the same passes through the reel part D, for example a calendar roll (See FIG. 1).

[0164] The results of experiments conducted with core raw paper by changing in many ways the spraying condition of the dispersion in the method of producing core raw paper of the present invention will be shown below by the examples of carrying out.

[0165] It should be noted, however, that the present invention is not limited to the following examples of carrying out.

[0166] The core raw paper used in the experiment was produced with the following conditions.

[0167] [Paper Making Conditions]

[0168] Paper machine: Ultraformer (made by K.K. Kobayashi Seisakusho)

[0169] Description of paper made: Normal core

[0170] Quantity per tsubo: 160 g/m²

[0171] Paper making speed: 300 m/min. or 600 m/min.

[0172] Width of paper: 4 m or 5 m

[0173] [Spraying conditions]

[0174] Place of spraying: The last drier on the upper row (See FIG. 2-C8) or the paper roll (See FIG. 2-D2)

[0175] Method of spraying: 1, 5, 10 or 20 cm³/min. respectively (5, 25, 50 or 100 cm³/min. respectively) are sprayed from 4 nozzles for a paper width of 4 m, and from 5 nozzles for a paper width of 5 m.

[0176] Rotating speed: 2 m/min.

[0177] Solid lubricant: Molybdenum disulfide [1 weight %]

[0178] Metal soap: Stearic acid soap [1 weight %]

[0179] Oils: Silicone oil [10 weight %]

[0180] In addition, all the wax used had respectively a melting point of 70° C. or below.

[0181] [Example of Carrying Out 1]

[0182] A dispersion containing 10 weight % of micro wax was sprayed over the last drier on the upper row for a total of 25 cm³/min so that 0.8 mg/m² of wax may be applied over a width of 5 m of core raw paper made at a speed of 600 m/min.

[0183] * Calculation formula: (25 g/min.×0.1)/(5 m×600 m/min.)=0.8 mg/m² (Calculated by assuming that relative weight is 1 g/cm³. Ditto hereinafter)

[0184] [Example of Carrying Out 2]

[0185] A dispersion containing 10% weight of a wax mixture consisting of equal amounts of paraffin wax and polyethylene wax was sprayed over the last drier on the upper row for a total of 50 cm³/min. so that 1.7 mg/m² of wax may be applied over a width of 5 m of core raw paper made at a speed of 600 m/min.

[0186] [Example of Carrying Out 3]

[0187] A dispersion containing 10% weight of a wax mixture consisting of equal amounts of paraffin wax and micro wax was sprayed over the last drier on the upper row for a total of 50 cm³/min. so that 4.2 mg/m² of wax may be applied over a width of 4 m of core raw paper made at a speed of 300 m/min.

[0188] [Example of Carrying Out 4]

[0189] A dispersion containing 25% weight of micro wax was sprayed over the last drier on the upper row for a total of 100 cm³/min. so that 8.3 mg/m² of wax may be applied over a width of 5 m of core raw paper made at a speed of 600 m/min.

[0190] [Example of Carrying Out 5]

[0191] A dispersion containing 20% weight of paraffin wax was sprayed over the last drier on the upper row for a total of 50 cm³/min. so that 8.3 mg/m² of wax may be applied over a width of 5 m of core raw paper made at a speed of 600 m/min.

[0192] [Control 1] (An Example of Excessive Application of Wax)

[0193] A dispersion containing 50% weight of micro wax was sprayed over the last drier on the upper row for a total of 100 cm³/min. so that 16.7 mg/m² of wax may be applied over a width of 5 m of core raw paper made at a speed of 600 m/min.

[0194] [Control 2] (An Example of Too Few Application of Wax)

[0195] A dispersion containing 5% weight of micro wax was sprayed over the last drier on the upper row for a total of 5 cm³/min. so that 0.08 mg/m² of wax may be applied over a width of 5 m of core raw paper made at a speed of 600 m/min.

[0196] [Control 3] (An Example of Excessive Application of Wax)

[0197] A dispersion containing 40% weight of paraffin wax was sprayed over the paper roll for a total of 100 cm³/min. so that 13.3 mg/m² of wax may be applied over a width of 5 m of core raw paper made at a speed of 600 m/min.

[0198] [Control 4] (An Example of Too Few Application of Wax)

[0199] A dispersion containing 5% weight of paraffin wax was sprayed over the paper roll for a total of 5 cm³/min. so that 0.08 mg/m² of wax may be applied over a width of 5 m of core raw paper made at a speed of 600 m/min.

[0200] [Control] [Ordinary Method of Production (Blank)]

[0201] Core raw paper was produced without any wax at all under the condition of a width of 5 m and a paper making speed of 600 m.min.

[0202] [Friction Experiment]

[0203] The friction coefficient (angle of starting to slide) for each of the core raw paper used in the examples of carrying out 1-4 and the controls 1-3 was measured on the experimental basis in accordance with the inclination method set forth in JIS P8147, and for each of them the angle of starting to slide between the face sides and between the back sides was measured.

[0204] The results of the first and fifth measurements are shown in the form of differences with the results of the control 5 (for the control 5, experimental values) in Table 1. TABLE 1 Paper Quantity Quantity Face-face Back-back width Speed sprayed Concentration applied (time) (time) (m) (m/min) (cm³/min) (%) (mg/m²) First Fifth First Fifth Remark Example 1 5 600 25 10 0.8 −2.5 −3.0 −0.5 −1.0 Example 2 5 600 50 10 1.7 −3.0 −3.5 −1.0 −1.5 Example 3 4 300 50 10 4.2 −3.5 −4.0 −1.5 −1.5 Example 4 5 600 100 25 8.3 −3.5 −4.0 −1.5 −2.0 Example 5 5 600 50 20 3.3 −3.0 −4.0 −1.0 −1.5 Control 1 5 600 100 50 16.7 −3.5 −4.0 −2.0 −2.0 Amount applied too much Control 2 5 600 5 5 0.08 −0.5 −1.0 + −0.5 Amount applied −0 too little Control 3 5 600 100 40 13.3 −3.5 −4.0 −2.0 −2.5 Amount applied too much Control 4 5 600 5 5 0.08 −0.5 −1.5 −0.5 −0.5 Amount applied too little Control 5 5 600 — — — 21.5 19.5 20.0 18.0 Blank

[0205] [Results]

[0206] In comparison with the control 5, most of the core raw paper coated with wax showed a smaller angle of starting to slide.

[0207] In other words, they showed a smaller frictional resistance.

[0208] However, in the cases where the amount of wax applied was 4.2 mg/m² or more (Examples of carrying out 3 and 4 as well as Control 1), an increase in the amount of wax applied brought about almost no difference in the angle of staring to slide.

[0209] [Measurement of the Consumption of Driving Power and Noises of the Corrugation Rolls]

[0210] The core raw paper used in the Examples of carrying out 1-4 and the Controls 1-3 was respectively lead through the corrugator (made by Mitsubishi Heavy Industry Co., Ltd. 50E), and the consumption of the driving power and noises of the corrugating roll was measured under the conditions of paper width of 1 m, and a gluing speed of 150 m/min.

[0211] During this measurement, the corrugated core was tainted with a black stripe and the liner was also tainted because the wax that transferred onto the corrugating roll was carbonized in an experiment using the Control 1.

[0212] And due to an excessive application of wax, a gluing defect by a gluing roll developed.

[0213] In the Control 3 also an almost identical situation developed.

[0214] Accordingly, with regards to the Controls 1 and 3, the production of corrugated boards by using said corrugator was suspended, and was excluded from this experiment and the successive experiments.

[0215] In other examples, there was no case of carbonization nor anything similar.

[0216] The results of measurement are shown in Table 2. TABLE 2 Quantities applied Power consumption Difference with Control 5 (Blank) Voice (mg/m²) (KW) (KW) (Phone) Difference with Control 5 Example 1 0.8 13.6 −0.6 103 −4 Example 2 1.7 13.5 −0.7 101 −6 Example 3 4.2 13.4 −0.8 101 −6 Example 4 8.3 13.4 −0.8 101 −6 Example 5 3.3 13.4 −0.8 100 −7 Control 1 — — — — — Control 2 0.08 14.1 −0.1 106 −1 Control 3 — — — — — Control 4 0.08 13.9 −0.3 105 −2 Control 5 — 14.2 — 107 —

[0217] [Results]

[0218] The consumption of driving power was smaller in the Examples of carrying out 1-5 in comparison with the Control 5, but it was not much different in the Controls 2 and 4.

[0219] And noises were also smaller in the Examples of carrying out 1-5, but they were not much different in the Controls 2 and 4.

[0220] [Tests of Corrugation Cracking and Corrugation Cutting]

[0221] When the core raw paper described in the Examples 1-5 and the Controls 2, 4, and 5 was lead through the corrugator (made by Mitsubishi Heavy Industries Ltd., 60G) and when its gluing speed was raised, sometimes corrugation cracking and corrugation cutting occurred.

[0222] [Results]

[0223] In the Control 5, corrugation cracking sometimes occurred at a gluing speed of 300 m/min. The core raw paper described in the Examples of carrying out 1-5, however, showed no case of corrugation cracking even when its gluing speed was raised up to 390 m/min.

[0224] And the core raw paper described in the Control 2 sometimes developed a corrugation cracking at a speed of 330 m/min, and in all the experiments conducts (five experiments), there developed corrugation cracking before a speed of 390 m/min. was reached.

[0225] Furthermore, the core raw paper described in the Control 4 sometimes developed a corrugation cracking at a speed of 350 m/min, and in four of the five experiments conducted there developed a corrugation cracking before a speed of 390 m/min. was reached, but in another experiment no corrugation cracking developed even at the speed of 390 m/min.

[0226] [Wearing Tests for the Corrugating Roll]

[0227] After passing the core raw paper described in the Examples of carrying out 1-5 and the Control 5 through the corrugator (made by Mitsubishi Heavy Industries Ltd., 50E) and after 1,000 hours and 2,000 hours of operating the same corrugator under the conditions of a paper width of 1 m and gluing speed of 150 m/min., a carbonless duplicating paper is inserted into the corrugating roll to examine the wearing of the corrugating roll.

[0228] Incidentally, it is possible to visualize the extent to which the corrugating roll is worn out by the intensity of shade made on the carbonless duplicating paper.

[0229] [Results]

[0230] In any one of the examples of carrying out described above, the carbonless duplicating paper showed a uniform shade of color (in other words, there was no change in pressure depending on the locality of the corrugating roll and the pressure was uniform.)

[0231] Therefore, almost no wearing occurred.

[0232] In the Control 5, in a test conducted after 1,000 hours of operation, the vicinity of both edges of the carbonless duplicating paper already showed a somewhat darker shade than at the center (in other words, the central part of the corrugating roll began wearing out), and after 2,000 hours of operation this could be confirmed remarkably.

[0233] By summarizing the results from the foregoing experiment, it is judged that the preferable amount of wax with which core raw paper is coated is in a range of 0.1-10 mg/m².

[0234] In spite of the description of the present invention that has been made so far, it is needless to say that the present invention is not limited to the examples of experiments and that a wide variety of other variations are possible provided that they do not deviate from its basic principle.

[0235] For example, in the present specification, the case of spraying the dispersion over the last drier of the upper row was described. However, it is obviously possible to adopt the last drier of the lower row or a combination of a plurality of driers such as the last driers of the upper and lower rows.

INDUSTRIAL APPLICABILITY

[0236] The present invention relates to core raw paper for corrugated boards and the method of producing the same. However, it can be applied generally to the whole field of paper making technology and similar effects can be expected provided that nothing deviates from its basic principle. 

1. Core raw paper for corrugated boards coated with wax on the face and the back wherein the amount of wax applied on said core raw paper is in a range of 0.1-10 mg/m².
 2. Core raw paper for corrugated boards according to claim 1 wherein the moisture content of said core raw paper is less than 10% when wax is applied.
 3. Core raw paper for corrugated boards according to claim 1 wherein a dispersion containing wax is sprayed over the last drier of the paper machine and the wax contained in said dispersion is transferred and applied on core raw paper.
 4. Core raw paper for corrugated boards according to claim 1 wherein the dispersion containing wax is sprayed over a paper roll of the paper machine and the wax contained in said dispersion is transferred and applied on core raw paper.
 5. A method of producing core raw paper for corrugated boards coated with wax using a paper machine provided with a plurality of groups of driers wherein a dispersion containing said wax is sprayed over the surface of the driers, the wax is oil-changed on the surface of the heated driers, and the oil-changed wax is transferred from the surface of the driers onto the face of core raw paper.
 6. The method of producing core raw paper for corrugated boards according to claim 5 wherein said driers are the driers belonging to the last group of the paper machine.
 7. The method of producing core raw paper for corrugated boards according to claim 5 wherein said driers are the last driers of the upper or lower rows among the driers belonging to the last group.
 8. The method of producing core raw paper for corrugated boards according to claim 5 wherein the melting point of said wax is lower than the surface temperature of the driers.
 9. A method of producing core raw paper for corrugated boards coated with wax by using a paper machine provided with a paper roll wherein a dispersion containing said wax is sprayed over the surface of said paper roll and said wax is transferred from the surface of said paper roll onto the face of core raw paper.
 10. The method of producing core raw paper for corrugated boards according to claim 5 or claim 9 wherein said wax is applied in such a way that the amount of wax applied to core raw paper would be in a range of 0.1-10 mg/m².
 11. The method of producing core raw paper for corrugated boards according to claim 5 or claim 9 wherein the moisture content of said core raw paper is less than 10% when the dispersion containing wax is sprayed.
 12. The method of producing core raw paper for corrugated boards according to claim 5 or claim 9 wherein said wax, after having transferred onto the face of core raw paper, partially is transferred to the back of core raw paper by the winding of core raw paper.
 13. The method of producing core raw paper for corrugated boards according to claim 5 or claim 9 wherein for said wax paraffin wax, polyethylene wax or micro wax is used singly or in combination.
 14. The method of producing core raw paper for corrugated boards according to claim 5 or claim 9 wherein said dispersion further contains a solid lubricant or a metal soap.
 15. The method of producing core raw paper for corrugated boards according to claim 5 or claim 9 wherein said dispersion further contains oils.
 16. A method of producing core raw paper for corrugated boards coated with wax by using a paper machine provided with a plurality of driers wherein the dispersion containing wax is sprayed over the surface of heated driers in the area where the moisture content of core raw paper passing through the paper machine is less than 10%, the wax is changed into oil on the surface of the heated driers, the oil-changed wax is transferred from the surface of the driers onto the face of core raw paper so that the quantity of wax applied to core raw paper may be in a range of 0.1-10 mg/m².
 17. A method of producing core raw paper for corrugated boards coated with wax by using a paper machine provided with a paper roll wherein the dispersion containing wax is sprayed over the surface of the paper roll, the wax is transferred onto the face of core raw paper with moisture content of less than 10% so that the quantity of wax applied to core raw paper may be in a range of 0.1-10 mg/m².
 18. A wax or a dispersion containing wax applied on core raw paper for corrugating boards wherein the same is applied on core raw paper for corrugating boards described in claim 3 or
 4. 19. A wax or a dispersion containing wax used in the method for producing core raw paper for corrugating boards wherein the same is used in the method for producing core raw paper for corrugating boards described in claim 5 or 9 